Interconnects between transmission lines, and between a transmission line and a circuit structure, such as a lumped element or a substrate component, may produce interference and/or be subject to interference from other circuits. Shielding may reduce interference between communication signals carried on different transmission lines and other circuit structures. A coaxial cable is a transmission line in which an outer conductor that surrounds an inner conductor provides shielding. Such coaxial cables require separate mechanical interconnects that match the cable configuration. Various other forms of transmission lines have been developed that are formed on or in circuit boards. These include microstrip and other strip lines, slot lines, coplanar waveguides, and the like. These transmissions lines, as well as other circuit components are generally not shielded, with the result that evanescent electromagnetic fields may be produced that can interfere with the operation of other circuit components.